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Bandwidth looks like a commodity today, but it still is not as free as air. Companies need more and more bandwidth in their networks and the associated cost can rapidly raise out of some target limits of cost containment. We will discuss the needs and ask you the question : what do you expect to get in the framework of bandwidth on demand ?

Bandwidth can be defined in different ways. For some is the speed at which you can transmit data across a line, called the bitrate. For some, it is the amount of data you can get across it, the throughput. Throughput is lower than speed, but not the reverse. But throughput is typically a few percent points lower than the rate of transmission, since every communications protocol has some overhead. For example, with Ethernet, you cannot get above 90% (according to Wikipedia). With bandwidth in the LAN, you can dimension it freely, as you own the cabling and the switching devices. You invest once, and you can consume as much as you can. For the WAN, it is different, since the connectivity is owned by the operator, who makes you pay for a certain bandwidth (speed). If you can estimate your needs well, you typically take the connection with the required bandwidth, but no more, otherwise you pay too much. In some cases, bandwidth is irregular or unpredictable. For example when you interconnect two datacenters, or big sources and sinks of data. In these cases there is an average bandwidth during some periods and high peaks of bandwidth at some other moments (for instance at the moment you do a backup, or during a telepresence video conference). In these cases you try to get a contract with the provider to cover the average speed and burstable speed, in function of your needs.

Thank you very much for your time and effort. We will present the results beginning of April.